The effects of stabilizers on the bath stability of electroless Ni deposition and the deposit

Electroless nickel (EN) deposition bath is known to have a major problem of sudden bath decomposition, which results in an increase in the operating cost of the process and the generation of environmentally hazardous waste. Bath stabilizers are normally added to extend its life. In this paper, the effects of two electroless nickel bath stabilizers; thiourea and maleic acid were investigated. The EN deposits were characterized in terms of surface morphology, microstructure, phase, and composition. It is demonstrated that the addition of thiourea and maleic acid significantly improved the stability of the EN bath. It was observed that the stabilizers have a minor and a major effect on phosphorus content and morphology of the EN deposits, respectively. It is also shown, for the first time, that the addition of the stabilizers has an effect on the nano-grain size of the EN deposit. (C) 2004 Elsevier B.V. All rights reserved.